Disordered alloys with short-range order: A Korringa-Kohn-Rostoker formulation within the cluster coherent-potential approximation

Publisher Website
Google Scholar
Abstract
We present a generalization of the Korringa-Kohn-Rostoker cluster coherent-potential approximation for systems with short-range order (SRO). For this purpose we have used the generalized augmented-space formalism of Gray and Kaplan, in which one can deal with independent (corresponding to purely random systems) as well as dependent (corresponding to systems with SRO) random variables. The expression for the configuration-averaged Green’s function in this case is essentially an expansion about the Green’s function for a purely random system, and contains an infinite number of terms. For simplicity, we truncate the series after the second-order correction term. Using this approximation, we have calculated the density of states (DOS) for a one-dimensional muffin-tin alloy with Markovian-type SRO and find that the introduction of SRO can produce large changes in the DOS. We also find that the approximation yields non-negative DOS at all energies for a reasonably wide range of SRO parameter.